Electronic devices, including semiconductor chips, are typically covered by or encapsulated within a sensor package to protect the electronic devices from undesirable conditions. Such undesirable conditions include light, heat, humidity, dust, and physical shock. In many sensor applications, the sensors directly interact with the environment being sensed and therefore require direct access to the sensed environment. Such sensors include gas-sensors, pressure sensors, bio-sensors, finger-print sensors, and humidity sensors. For these types of sensors, an “exposed-die package” is used which provides a packaging configuration which does not cover a predetermined area of the sensor and which includes the structure of the sensor providing the sensing function.
One common exposed-die package for sensors that require direct access to the sensed environment is a metal can package. Metal can packages provide access to the sensing area of the sensor and protect the sensor components, such as the silicon substrate and the bond wires, from mechanical impact. However, the use of metal can packages on some sensors results in a large packaging footprint since the can portion of the metal can package is typically glued to a seal-ring area of the sensor substrate. In addition, metal can packages often require a large height from the sensor substrate to provide sufficient clearance to the bond wires to prevent shorting therebetween. The fabrication and the assembly of the metal cap packages are also relatively costly compared to other packaging methods.
Mold packages are another type of packaging widely used in sensor applications and application specific integrated circuit (ASIC) and integrated circuit (IC) packaging since the mold packages provide a low cost package suited for high volume applications. Most mold packaging includes the use of a black plastic material, typically including epoxy molding compounds. One drawback of mold packages, however, is that it is sometimes difficult to keep the sensing area clear of mold material during the formation of the mold package.
Consequently, there is a need for an exposed-die mold package for sensors that is free of mold material in the sensing area of the sensors. A method of forming an exposed-died mold package for such sensors is also desirable.